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Appendix V.

983

of these can be presented upwards as required, by rotating the
hand wheel 27. The vertical rod 28 has inclined ends so
arranged that when the tappet 29 catches stop 26, and the stop
bar is moved bodily, a grooved projection upon it depresses the
rod 28, causing a bar 30 to move rightward, and so release the
trigger 23. The worm cradle 17 at" once falls, and the feed is
stopped. A clamp 31 fixes the head for heavy machining.

Both worm cradles must be dropped when the leading screw
is in gear. In Fig. 905, 32 is a slide carrying a half-nut 33,
which can be moved in a direction across the bed. When
lever. 34 is in the position shewn, the nut 33 is in gear with the
screw; but if 34 be lowered to a vertical position, it acts upon a
coarse-threaded screw at 35, and causes slide 32 to move towards
the operator, putting 33 out of gear with the leading screw.
Several different guide screws are provided with each lathe.

All the motions mentioned are so interlocked that it is
impossible for any two to be engaged simultaneously, a cam on
bolt 35A preventing more than one cradle being raised at a time,
and compelling both to drop before the screw can be put in gear.

The Hexagon Head and Saddle is illustrated in Figs. 905 and
906, Plate XIX., and in Fig. 909. The saddle is moved by hand
or power, the former by the 'pilot' wheel 36 through wheels 37,
40, 41 to the rack, and the latter from traverse shaft h^ through
spur wheels 42 and 43, worm wheel 38, and wheels 37, 40, 41 to
the rack. When hand traverse is required, the self-act is put out
of gear. At 44 (Fig. 909) is a notch on bar 45, shewn in plan
at 46, and when handle 46 is pressed rightward, the bar turns on
fulcrum 47, releasing stud 44-46, and causing the worm cradle to
be dropped. The traverse may also be stopped automatically.
At 49 are six bars fixed in suitable but independent positions by
the screws 50, and having notches near their left end, as at 51,
Fig. 909. There are six pawls 52, one to each bar, five of which
are always held up clear of the bar by means of the props 53.
One in turn, however, is allowed to rest on the bar, viz., that
corresponding to the pawl in action, this permission being granted
by the tup-shaped depression 54 on the hexagon head. As the
depressions are specially spaced as shewn in plan of the head,
Fig. 909, it is arranged that only the proper pawl shall drop into